A system of sharing an image forming apparatus by a plurality of information processors by connecting the information processors, such as personal computers, and the image forming apparatus, such as a printer and a multi-function machine, over a communication network has been proposed and introduced in offices, etc. This was realized by not only an increase in the speed of the image forming apparatus, but also a processing ability for receiving a plurality of jobs without a delay and forming images one after another, which is acquired by incorporating an internal storage device in the image forming apparatus.
Moreover, with an increase in the number of users on the communication network, a great importance is attached to the security of corporate data and personal data in outputting data according to an instruction from an information processor. Hence, a system was proposed to encrypt a print job to be transmitted between an information processor and an image forming apparatus over the communication network (see, for example, Japanese Patent Application Laid-Open No. 2002-342061). In addition, image forming apparatuses have started to include a so-called secure print function for temporarily delaying a print job received by an image forming apparatus and starting a print process upon authentication of a password from a user, etc.
Further, in recent years, image forming apparatuses include a storage device such as a HDD (Hard Disk Drive) device, thereby capable of temporarily storing print data to be processed. At this time, by making it difficult to read the print data by deleting the print data or overwriting random data upon completion of the print process, the confidentiality of print data is protected (see, for example, Japanese Patent Application Laid-Open No. 09-223061). Consequently, even if the internal storage device storing the print data is taken out by someone; it is possible to prevent the print data from being fraudulently taken out.